This invention relates generally to circuit breakers, and more particularly to circuit breaker thermal magnetic trip units and methods.
Circuit breakers typically include one or more electrical contacts, and provide protection against persistent over-current conditions and short circuit conditions. In many circuit breakers, a thermal-magnetic trip unit includes a thermal trip portion which trips the circuit breaker on persistent over-current conditions, and a magnetic trip portion which trips the circuit breaker on short circuit conditions. Existing thermal-magnetic trip units typically include a single trip bar that releases a trip mechanism to trip the circuit breaker and open the electrical contacts to stop the flow of current in the protected circuit.
However, existing thermal-magnetic trip units typically do not isolate thermal trip events from magnetic trip events.